It is known that a flight phase, such as for example a climb phase on takeoff and an approach phase on landing, concentrates a relatively significant number of piloting steps to be followed for the pilot. The actions to be executed, decisions to be taken and monitoring to be ensured during these piloting steps together generate a significant workload. This load is furthermore increased in case of degraded conditions (meteorology, traffic, breakdown, etc.). By way of example, these actions may be:
on takeoff:                reduction in the thrust after initial climb;        retraction of the landing gears; and        retraction of the lift-enhancing systems during the acceleration phase;        
on landing:                extension of the landing gears and of the lift-enhancing systems so as to progressively dissipate the energy and put the aircraft in a landing configuration; and        in case of precision approach required by poor visibility, a monitoring of the approach and a decision taking as regards whether to continue the approach or to go around as a function of the visibility level observed on passing a predefined height relative to the ground (called the decision height).        
The instants of executions of actions or of taking of decisions are indicated to the pilot by a display most of the time in head-down mode on a standard screen of “PFD” (“Primary Flight Display”) type, via a speed scale for the changes of configuration in particular, via an altitude scale for the thrust reduction on takeoff, or via a display of the height relative to the ground for the decision height in a precision approach.
The crew must therefore continually monitor these flight parameters (generally displayed in head-down mode on the PFD), while looking outside the cockpit to pilot the aircraft or monitor the progress of the approach and the available visibility level. The crew must therefore go to and fro visually between information displayed head-down decoupled from the outside and a monitoring of the outside environment for the piloting or monitoring tasks. In order to facilitate the pilot's task, it would be desirable to avoid such toing and froing.
Moreover, situation awareness, i.e. knowledge about the situation of the flight phase with different piloting steps with respect to the current situation, requires a complex mental process, in the course of which the crew must analyze information decorrelated from the outside environment (information regarding height or speed displayed on a screen in the cockpit) within the framework of active monitoring of the environment of the aircraft so as to take decisions (for example to cancel or continue the approach).